Downhole motors (colloquially known as “mud motors”) are powerful generators used in drilling operations to turn a drill bit. Downhole motors are often powered by a drilling fluid, such as mud, which is also used to lubricate the drill string and to transport cuttings and particulate matter away from the borehole.
A downhole motor may act as a positive displacement motor (PDM) in which a drilling fluid pumped through the interior converts hydraulic energy into mechanical energy to turn a drilling bit, which has applications in well drilling. A positive displacement motor propels the drilling fluid by means of the progress of a set of cavities in the interior of the motor. A positive displacement motor typically includes a helical rotor disposed within a stator, where the rotor seals tightly against the stator as it rotates to form a set of cavities in between. As the rotor rotates within the stator, the cavities move and the drilling fluid in the cavities is pumped through the assembly.